1. What is Ankle Brachial Index?

The Ankle Brachial Index (ABI) is a simple, non-invasive test that compares the blood pressure in the upper and lower limbs to assess peripheral arterial disease (PAD). It's calculated by dividing the systolic blood pressure at the ankle by the systolic blood pressure in the arm.

2. How Does the Calculator Work?

The calculator uses the ABI formula:

Where:

• Ankle Pressure — Highest systolic pressure from either posterior tibial or dorsalis pedis artery (mmHg)
• Brachial Pressure — Highest systolic pressure from either arm (mmHg)

Interpretation:

• ABI > 1.3: Possible calcified vessels (non-compressible)
• 0.9-1.3: Normal
• 0.7-0.9: Mild arterial disease
• 0.4-0.7: Moderate arterial disease
• <0.4: Severe arterial disease

3. Importance of ABI Measurement

Details: ABI is a quick, reliable method to screen for PAD. Low ABI values correlate with increased cardiovascular risk and mortality. It helps determine disease severity and guide treatment decisions.

4. Using the Calculator

Tips: Enter the highest systolic pressure from either ankle and the highest systolic pressure from either arm. Both values must be greater than 0 mmHg for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: Which ankle pressure should I use?
A: Use the higher of the two ankle pressures (posterior tibial or dorsalis pedis) from each leg. The lowest ABI from either leg determines PAD severity.

Q2: Why might ABI be >1.3?
A: Values >1.3 suggest non-compressible arteries, often due to medial calcification (common in diabetes, CKD, or elderly patients).

Q3: How often should ABI be measured?
A: For PAD patients, annually or with symptom changes. For high-risk patients without PAD, every 2-5 years depending on risk factors.

Q4: Can ABI be used during pregnancy?
A: ABI interpretation may be less reliable during pregnancy due to hemodynamic changes. Clinical correlation is essential.

Q5: What's the toe-brachial index (TBI)?
A: TBI uses toe pressure when ABI is unreliable (e.g., non-compressible vessels). Normal TBI is ≥0.7.